Needs for flat panel displays are now growing in the advance information society. The flat panel displays such as a non-self-emitting LCD (liquid crystal display), a self-emitting PDP (plasma display panel), an inorganic EL (electroluminescent) display, and an organic EL display, are known. Particularly, the organic EL display is making remarkable progress.
The organic EL element, which is attracted attention as a next-generation light-emitting element, includes at least an organic light-emitting layer between a pair of electrodes, and if necessarily, further includes a charge injecting layer that injects charges into the light-emitting layer and a charge transporting layer that transports charges from the electrodes to an organic layer. This organic EL element can be reduced in its thickness and weight and has characteristics such as low-voltage driving, high luminance, and self-light emission. Such an organic EL element is now actively being researched and developed.
As a method of forming the organic EL element, deposition of organic materials or application thereof by an ink-jet process and the like, may be mentioned. For example, Patent Document 1 discloses a method in which an anode electrode and a light-emitting layer are formed in each pixel, and a hole transporting layer, an electron transporting layer, and a cathode electrode are formed in continuity in a plurality of pixels, as the method of forming films constituting an EL element by deposition. In this case, the light-emitting layers in respective pixels are separated from one another not by a bank but by being formed with a mask and a vacuum-deposition apparatus, and the like. So it is difficult for such a method to be applied to a large-sized organic EL display device. Further, such a method has room for improvement in productivity and cost effectiveness.
For example, Patent Document 2 discloses a method of applying materials constituting an organic EL element by an ink-jet process. According to such a method, a multi-layer of a hole injecting layer and a light-emitting layer, which constitutes an organic EL element, is applied in a region between banks. The hole injecting layer, which has conductivity, is exposed if it is applied in a larger region than that of the light-emitting layer arranged thereabove. In such a case, a leakage current having no contribution to light emission might be generated if a cathode electrode is formed on the light-emitting layer.
For example, Patent Document 3 discloses a method of suppressing such a leakage current in an organic EL element including a multi-layer structure of a hole injecting/transporting layer and a light-emitting layer, these layers being formed so that the area for deposition of the light-emitting layer is equal to or greater than the area for deposition of the hole injecting/transporting layer.
In addition, for example, Patent Document 4 discloses a method of providing a bank surface with non-affinity greater than that of a film surface in a region between banks, thereby stacking flat films in the region between the banks, as a method of forming layers constituting an organic EL element so that the thickness of the respective layers is uniform. Further, for example, Patent Document 5 discloses a method of hindering an organic EL material from migrating from one space between banks to another by providing a bank top surface with a lyophobic treatment.
In addition, for example, Patent Document 6 discloses that a substrate surface on which a light-emitting layer is to be formed is provided with a lyophobic treatment, as a way of forming a light-emitting layer without forming a bank in an EL element-forming method involving application of liquid materials.
With respect to a manufacture of a color filter by an ink-jet process, for example, Patent Document 7 discloses that a projection for partitioning pixels has an ink-repellent top surface. According to this method, it can be possible to prevent an ink that has been injected into one pixel region from spreading into another or bleeding.
[Patent Document 1]
    Japanese Kokai Publication No. 2004-6362[Patent Document 2]    Japanese Kokai Publication No. 2000-323276[Patent Document 3]    WO 01/074121[Patent Document 4]    WO 99/48339[Patent Document 5]    Japanese Kokai Publication No. 2004-55159[Patent Document 6]    Japanese Kokai Publication No. 2002-124381[Patent Document 7]    Japanese Kokai Publication No. Hei-09-203803